In-ear monitors.
The following in-ear monitors use the MMCX connector, which I find more forgiving on new users than the 2-pin connector;
TINHIFI T2 Plus
US$ 60
BASN Bmaster
US$ 83-93
7HZ Timeless
US$ 199-224
Etymotic Research ER4XR
US$ 230-350
Sony IER-Z1R
US$ 1700-2000
